Polymerization of 2-diethylamino-1,3,2-dioxaphosphorinane, 2. Kinetics

Kinetic studies of the anionic polymerization of 2-diethylamino-1,3,2-dioxaphosphorinane were performed in THF solution with (CH₃)₃SiO^?K⁺ as initiator at temperatures close to r.t. Initiation involves nucleophilic attack of the anion on P atom in the monomer molecule. Breaking of the P? O bond leads to an alcoholate anion as the growing species. Polymerization was shown to proceed via macroion-pairs and to be nearly living; e.g. at r.t. for every 250 propagations there is one termination. Rate constant of propagation k = 3,4 ± 0,31·mol^?1·s^?1 at 25°C, ΔH = 13,3 kcal·mol^?1 and ΔS = ?32,2 cal·mol^?1·K^?1. The ratio k/k was determined by solving a kinetic scheme involving propagation and termination. It was shown that termination consists in the alcoholate anion attack on P in either polymer or monomer molecule with expulsion of (C₂H₅)₂N^? anion and formation of a P? O bond. The dialkylamide anions cannot reinitiate polymerization. In solving the kinetic scheme it was assumed that termination involving both polymer and monomer proceeds with rate constants equal to each other.